Eight years later your post I have the game box here on my laps.
It says WWI 1914 and A&A game. So they didn’t really call it Axis and Allies. The game is super cool and since I am a great fan of the The Great War I have to say that I enjoy it even more than the other ( so far I have playes only anniversary). Kind regards. Meerko

Welcome, blindingblizzard!
@blindingblizzard:
The rules state that U.S. ships cannot move into contested sea zones.Â
There is no such thing as a contested sea zone. The rule states that the US may not move units into a contested territory. (For clarifications on this, see the FAQ thread.)
In your example, Germany may choose to either include the US ships in its attack, bringing the US into the war, or ignore them.